#include <stdio.h>
int a[1000000];

int calculare(long n,int a[1000000]){
	int nr=1,i,j;

	for (i=2;i<=n;i++)
		a[i]=i;
	a[1]=0;

	for (i=2;i<=n;i++){
		if (a[i]==i)
			for (j=i;j<=n;j+=i)
				a[j]-=a[j]/i;
		nr+=a[i];
	}


	return 2*nr;
}
int main()
{
	FILE* f=fopen("fractii.in","r");
	FILE* g=fopen("fractii.out", "w");
	long n;

	fscanf(f,"%d", &n);
	fprintf(g,"%d",calculare(n,a));

	fclose(f);
	fclose(g);
	return 0;
}